


The Fever of Battle

by stormysgambit



Category: Haikyuu!!
Genre: Character Death, Enemies to Lovers, M/M, Whirlwind Romance, anthropomorphic cells, i don't know what we want to call this but it sure is a time, microbiology is fun
Language: English
Status: Completed
Published: 2020-12-15
Updated: 2020-12-15
Packaged: 2021-03-10 19:14:27
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 1
Words: 3,091
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28082235
Author URL: https://archiveofourown.org/users/stormysgambit/pseuds/stormysgambit
Summary: In the midst of a pneumonia infection, a memory B cell named Tooru and a Staphylococcus pneumoniae cell named Hajime find themselves drawn to each other and falling in love
Relationships: Iwaizumi Hajime/Oikawa Tooru
Comments: 7
Kudos: 16
Collections: IwaOi Week 2020





	The Fever of Battle

**Author's Note:**

> for kay, who told me I should in fact write this when I was still wondering why this was a thought I even had  
> thank you for allowing me endlessly spam you with my thoughts <3

Things had been fairly quiet in the body for the last several months. A memory B cell by the name of Tooru was circulating through the bloodstream when he received the signal, his antigen receptors vibrating. It had been a while, but one of their most familiar foes was back. _Staphylococcus pneumoniae_.

Antigen receptors stimulated, Tooru began to arm himself with antibodies to aid in the fight against the infection as he raced off to the lungs. He surveyed the lungs when he arrived, observing several clusters of the bacteria scattered throughout the alveoli. At the moment, the bacteria appeared to have the upper hand. Looked like they were going to be in for quite the battle. Hopefully their backup would arrive soon.

Tooru’s receptors vibrated again, and he lowered his gaze, hair falling across his eyes while he loaded up his antibodies, preparing to attack his target. His reflexes were honed, making him aware of even the slightest movement around him. He loaded the antibodies into the quiver on his back, gripping his bow. He turned around in a slow circle, making sure he had given the bacteria no room to surround him. That was when Tooru spotted him. Standing off to the side, clad all in black, watching the battle unfold, arms crossed, an amused look on his face. He wanted to wipe that look of the bacteria’s face. Permanently.

Tooru had been in a few battles against _S. pneumoniae_ , before, so he knew what to expect. He preferred range fighting, hitting the foe with his antibodies from across the battlefield, then going in for the kill with the daggers he used for close combat if necessary. He was more than capable of handling himself. And yet...

Against his better judgment, Tooru decided to engage the bacterium. Not his usual style. He preferred to wipe them out as quickly as possible, don’t allow them to multiply. He wandered over to the _Staphylococcus_ cell, daggers gripped tightly, ready to wipe him out in one smooth motion. As he grew closer, his antigen receptors reacted again and Tooru bristled. This was one of his targets, all the better. He couldn’t put his finger on it, but something about this particular bacterial cell really irked him. “You picked the wrong lungs to settle in,” he proclaimed, tapping the cell on the shoulder, placing one of his daggers against his opponent’s throat.

The cell turned around and...Oh. Tooru faltered, hands dropping back to his sides. He felt himself go weak, when he gazed upon the sharp jawline and scowling brow above enticingly calm and collected green eyes. Looked like he had found a seasoned veteran, at least as far as bacterial cells went. He licked his lips and swallowed as his eyes swept over the cell’s broad shoulders and down his arms.

Hajime had been one of the leading cells of the infection. He’d instructed the other cells on where to go as they divided, watching with satisfaction as their numbers increased. The arrival of the first B cells had been a problem, but there didn’t seem to be too many of them. He was fairly confident that he and his fellow _Staphylococcus_ army would concur these lungs.

Was being the operative word. Until just now, when he felt the sharp point of steel against his neck and turned around to find himself face to face with one of the B cells, armed to the teeth with antibodies, glaring at him in rage. Hajime couldn’t help but notice that even with his face all screwed up like that, said cell was quite attractive. Hajime found the way his nose was currently scrunched up particularly endearing.

“I wouldn’t be too sure about that,” Hajime replied, uncrossing his arms with a smirk. “You guys appear to be the ones who are struggling from where I’m standing.”

“And I wouldn’t be too sure about that,” Tooru mocked, fingering at his antibodies and raising the dagger again. “Any minute now, our backup is going to arrive, and you’ll all be wiped out.” Tooru’s job was simple. All he had to do was release the antibodies, and that would target this cell for destruction. And yet, for some reason, he couldn’t bring himself to do it. Something about this particular _Staph_ cell was throwing him off his guard. It might be those ridiculously well developed arms of his. Or the slightly lopsided nature of his grin as he teased Tooru, which softened his otherwise intense face. Or maybe it was the air of utter confidence. If he weren’t the enemy...Tooru shook his head. He was the enemy. It was in their nature to throw you off, make you forget your job. Tooru wasn’t about to fall for his trap.

“Gosh you’re adorable when you’re all pouty like that,” the _Staph_ cell told Tooru, grabbing ahold of Tooru’s face, squishing his cheeks, grinning as Tooru’s face flushed and his eyes widened. “I’ll see you around. Name’s Hajime,” he added, before sauntering off into the battlefield. If Tooru stared after him, admiring the way his back muscles moved as he walked, well, no one could blame him.

Tooru pressed a hand to his face, staring after Hajime, eyes narrowed. His target now had a name, next time he wouldn’t be so lucky. He knew he should take aim, target Hajime while his back was turned, but Tooru made up his mind that when they did engage in battle, it was going to be face to face. Rather than following him, Tooru spun on his heel and headed off in the opposite direction.

The battle raged on, cytotoxic T cells arriving to aid in the disposal of the bacterial cells. Mucus began to fill the floor of the lungs, making it difficult to navigate. As infection settled in the atmosphere grew warmer, fever. Various immune cells and bacterial cells were slumped on the ground, panting in exhaustion and from the heat. Some of the immune cells wouldn’t survive, they would either succumb to the infection or the fever, but not those who had fought similar battles before. A few casualties on their side was inevitable, what mattered was that the casualties on the side of the bacteria was greater, or even better, complete annihilation. Tooru had fought _Staph_ many times, so he wasn’t in as bad of shape as some of the younger memory cells, but he was still hot. He wiped his brow and his eyes landed on a familiar figure, once again on the edge of the battlefield.

The air of the lungs had risen a few degrees, and while it wasn’t unbearably hot yet, it was still unpleasant. Hajime panted slightly as he leaned against the wall, trying to stave off the fever. He was one of the strongest cells here, this surely wouldn’t be his end. He stiffened when he felt a tapping on his shoulder, drawing his sword. It was the same B cell as before, holding out a bottle of water.

“You’re helping me?” Hajime asked, raising an eyebrow as he accepted the bottle.

“I’m making sure you’re in top shape for when we battle each other,” Tooru retorted with a huff. “Don’t flatter yourself.”

“How noble of you, when you could just let me die here, which would make your job so much easier. Do I at least get to learn your name then? I already gave you mine.” Hajime unscrewed the cap and drank, waiting for a response. “It’s only fair,” he added when he was finished, tossing the bottle aside.

“I don’t owe you anything. You’re trying to infect our body. Don’t make the mistake of thinking we’re on the same footing.” Tooru crossed his arms over his chest, glowering.

“You say that,” Hajime responded, stepping closer and poking Tooru in the chest. “And yet here you are. Giving me aid. Wonder why that is.” He raised an eyebrow as Tooru’s mouth dropped open. Without waiting for a response, Hajime charged back into the fray, leaving Tooru gaping after him.

The fever intensified as the battle raged on, more mucus building up in the lungs, which now shook with each thunderous cough. Much as he hated to admit it, Tooru was in trouble. He had been helping some of the less experienced cells to escape to a safer part of the lungs when he found himself cornered by several of the bacterial cells, with no backup in site. To make matters worse, his antigens weren’t responding, making his antibodies useless. His daggers had been knocked away when one of them attacked from behind, so he was currently trying to fend all of them off barehanded, and he was slowly losing his stamina. Until Hajime showed up anyways. Then Tooru knew he was going to meet his demise here.

It looked like the _Staph_ might just conquer these lungs after all, Hajime thought to himself, eyes sweeping over the battlefield. He saw a cluster of his fellow bacteria surrounding a B cell, and sprinted over, ready to finish it off. He locked eyes with the cornered cell, whose eyes were full of resignation and defeat. His heart fluttered when he realized it was the same B cell he had run into twice now. He let out a roar, and threw himself into the fray, swinging his sword in a wide, sweeping arc, making quick work of the surrounding bacteria.

“Are you okay?” Hajime asked, glancing down at the B cell, whose leg appeared to be in bad shape.

“You saved me. From your own clan members,” Tooru gasped, stunned. His breathing was ragged, more from the pain than it was the fever.

“Just returning the favor from the other day. Looks pretty nasty,” Hajime replied, nodding at Tooru’s leg.

“It’s nothing, I can manage.” Tooru braced his hands against the floor of the lung, his leg shaking as he tried to stand. He grimaced as a wave of pain coursed through the leg, and his knees buckled. The _Staph_ cell, no, Hajime, appeared to be looking at him with concern, rather than malicious intent.

“Let me help you.” Hajime offered a hand, pulling Tooru up. “Come on, I’ll get you out of here to a more secluded spot.” He wrapped his arm around Tooru’s waist, supporting him. Tooru leaned into the firmness of Hajime’s grip, letting out a hiss of pain. He felt oddly reassured as Hajime dragged him across the battlefield, even though he knew he was likely to be finished off. If Hajime was the one to kill him, well, maybe that wouldn’t be so bad. He pressed closer to Hajime as they walked.

With his leg damaged, it was more difficult for Tooru to traverse his way through the thick phlegm coating the floor, even with Hajime’s aid. He stumbled and fell, crying out at the fresh wave of pain.

“Climb on,” Hajime told him, turning around and offering his back to Tooru.

Tooru felt his face burn, and he knew this time, it wasn’t from the fever. He wrapped his arms tightly around Hajime’s neck. He could feel how sweaty the fever was making Hajime, his breathing labored. He probably wouldn’t last much longer. Tooru was startled to realize this thought upset him.

Hajime deliberately made his way across the battlefield, bringing Tooru to the far edges, away from all the chaos. As the infection raged on, the cells had all migrated towards the center of the lungs. He gingerly set Tooru down on a section of the lungs that was blessedly dry. “I just saved your life. Surely you can tell me your name now, right?”

Tooru gazed warily back at the bacterium. His mind was still telling him that Hajime had brought him here to finish him off. If that were his goal though, surely he never would have come to Tooru’s aid in the first place. Tooru found he felt oddly relaxed. He hesitated still, studying Hajime’s face and finding nothing but honesty. “Tooru,” he offered at last, leaning back.

Hajime nodded and let out a low grunt before he began binding Tooru’s leg. Tooru watched with a puzzled expression.

“Hey...your hands…” Tooru uttered, reaching for Hajime’s hand, the skin rough and worn, the signs of a true battler. His hand was hot, Tooru noticed. The fever. The knuckles were all torn up and bloody. Hajime attempted to pull away, but Tooru’s grip was stronger than he expected. He looked up and saw that Hajime’s breathing was more labored than it should be for someone in his condition, confirming his suspicion. “You should be more careful,” Tooru whispered, running his thumb across the bloodied knuckles. He tore off a strip of gauze and carefully wrapped it around Hajime’s hand.

Tooru could feel his heart rate increase, a lump rising in his throat. Maybe the fever was beginning to affect him after all, he thought as he brought Hajime’s hand up to his lips, planting a tender kiss to the knuckles.

“I have to go.”

Tooru ignored the throbbing in his leg as he stood, he needed to be anywhere but here, he needed to get back onto the battlefield. He felt a tugging around his waist pulling him back down.

“Do you have to?” Hajime asked, dragging Tooru back down towards him, staring intently. Tooru’s eyes were wide and he was trembling. “Stay with me,” Hajime breathed, reaching out to brush a stray lock of hair out of Tooru’s eyes.

Tooru shuddered at the touch. Hajime’s hand was hot, far too hot. Tooru’s eyes fluttered open and he nodded, heart pounding now. He felt Hajime’s arm tighten around his waist, his other hand cupping his face. Hajime pulled Tooru closer, pausing when their faces were inches apart. His eyes were glazed over, burning from the fever. Hajime tilted Tooru’s face forward, pressing his lips against Tooru’s. Tooru’s eyes snapped closed, his arms clutched at Hajime as he eagerly kissed back.

The fever raged through the lungs while Tooru and Hajime lay on the floor, Tooru’s head on Hajime’s chest. Tooru could feel how shallow Hajime’s breath was beneath him. Hajime’s chest shuddered and fought for air. His hand slowly ran through Tooru’s hair as they listened to the sounds of the battle raging on. His other hand clutched Tooru’s, fingers loosely locked together. They lay there, trying to ignore the inevitable.

“Hajime?” Tooru turned his head, trying to ignore the twisting stab of pain in his heart when he saw how unfocused Hajime’s eyes were.

“Yeah?” Hajime’s hand stopped mid stroke as he turned to look at Tooru.

“Wouldn’t it be nice if we could just stay here forever?” Tooru pressed a kiss against Hajime’s chest, wishing it could ease some of his pain, and Hajime cradled him closer.

“It would,” Hajime agreed, a soft smile spreading across his face as he continued to stroke Tooru’s hair. His other hand squeezed Tooru’s.

Suddenly, the deafening wail of a siren sounded throughout the area. Tooru was well familiar with it, the siren meant they were close to defeating the bacteria. He bolted upright with a gasp. “Hajime you have to get out of here!” The siren sounded again. “NOW!” He cried, frantic, pulling Hajime to his feet. “Hajime, you have to run, they’re going to destroy you!”

Hajime turned his head, he could see more B cells and the advancing cytotoxic T cells. Flying through the air, he could make out the antibodies that would mark him for destruction. He turned to Tooru, eyes suddenly clear and hard. Hurt. “Tooru, did you signal them?”

Tooru watched the advancing swarm of immune cells and shook his head, tears in the corners of his eyes. “I didn’t, I would never do that, I swear!” He pushed on Hajime again, harder now. “I told you, you have to go!”

Hajime grabbed Tooru, pulling him in for one last kiss before he took off. His movement was slower and less steady than it had been a few days ago, he wouldn’t make it far in this condition.

“HAJIME RUN!” Tooru’s voice strained against his throat, tears warming his cheeks.

Hajime turned back at the sound of his voice and smiled at Tooru, and Tooru could feel his heart break. He watched a moment further before turning away. He couldn’t. He felt the antibodies rush past him, in the direction Hajime had headed. Tooru’s legs pumped furiously as he ran, trying to reach Hajime before the antibodies did.

Tooru was still running when the final siren sounded, signaling they had won. His eyes frantically scanned the battlefield, searching for Hajime. His leg screamed in agony, but this was minimal compared to the pain in his heart. Just when he had given up hope, he stumbled across Hajime’s fallen form, still alive, but barely.

“Hajime?” Tooru called out, dragging himself forward when his leg crumpled beneath him. He carefully made his way towards Hajime, who was breathing shallowly. “Hajime, I’m here, I’m here now.” He cupped Hajime’s face in his hands, rubbing his thumbs over Hajime’s cheeks, wet like his own.

Hajime cracked an eye open and smiled, reaching out for Tooru’s face. “Tooru,” He choked out, stroking Tooru’s cheek. It was the most clear his eyes had been in days.

“You’re going to be fine,” Tooru told him, hot tears spilling down his face, even though they both knew Hajime wouldn’t. Tooru took Hajime’s hand, feeling how weak Hajime’s pulse was. “You’re going to be fine,” Tooru repeated, pressing a kiss to Hajime’s forehead, before laying down next to him, holding his hand tightly.

The fever burned through the lungs for a few days more, but Tooru couldn’t bring his body to leave, even though he knew Hajime was gone. It was only when the cleanup crew arrived that Tooru finally allowed himself to move. He kissed Hajime one last time as he stood, cursing his job and his comrades.

He made his way to the exit, slowed down by his injured leg and the heaviness in his heart. He cast one last look back towards Hajime as he stood in the doorway to the bloodstream. He reached up to his face, brushing his fingers against the tears that fell there. He braced himself against the doorframe and pressed his fingers to his lips. He blew a kiss and turned back around, stepping through the door, wiping away the tears. No more time for tears now, back to work now, at least, that’s what he tried to tell himself.

**Author's Note:**

> You know you majored in biology when you're trying to think of a unique spin for the enemies to lovers trope. And this sure as heck is unique. I wrote a shorter version of this for IwaOi week, and wasn't planning on doing anything with it but then more people had interest than I thought, so here we are. For the sake of the work, look at them as anthropomorphic cells, kind of a "Cells at Work" type of scenario. I legitimately considered writing them as actual cells, because I am again a nerd. Could have gone either way, I did just write a thread on a sentient blue line last week, so...
> 
> This was also weird, since I tend to write in the present tense for the most part, but past tense felt more suitable here. 
> 
> So for IwaOi week 2020 Day 6: Enemies to lovers
> 
> You can find me on twitter at [stormysgambit](https://twitter.com/stormysgambit)


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